Part [1.—Stichodactyline and Zoanthee. 183 
epithelium, and in the latter is considerably folded in preserved material, the 
foldings being followed by the mesoglea. A cuticle is not distinguishable. 
The mesogloea is very variable in thickness, owing to its numerous foldings. 
It is remarkably clear and homogeneous; no fibrillar structure is indicated, and it 
is practically devoid of any structural elements, isolated celis occuring with 
extreme rarity. ven after the other structures of the polyps have been deeply 
stained the mesoglcea remains colourless and indistinguishable from the field of the 
microscope. The same phenomenon is presented throughout the polyp, and 
evidently throughout the genus, and is that characteristic of the mesoglcea of the 
Madreporaria. 
The endoderm of the base and column is scarcely narrower than the ectoderm, 
and gland cells with dense, highly-refractive contents, occur sparingly. Zooxan- 
thellae are absent throughout the polyp. The circular endodermal muscle is 
feebly developed in the base, but becomes stronger in the column, being sup- 
ported on small mesoglceal plaitings, and enlarges distally to form the sphincter 
muscle. 
The sphincter muscle (Pl. xm, fig. 3) is endodermal, and intermediate in 
character between a diffuse and restricted form. ‘The muscles fibres are very 
strong and closely arranged, and become concentrated on long mesoglceal pro- 
cesses; these latter, however, never become so long and branching as in @. viridis 
and (. carnea, but are stronger than those of C. australis. 
The knobs of the tentacles consist almost wholly of a very deep ectoderm ; 
the mesogleea and endoderm extend into them but a short distance, and they never 
exhibit any lumen. 
An outer broad zone of the ectoderm is largely made up of very long, narrow 
nematocysts showing the internal spiral thread distinctly. Occasionally a large, 
oval, stinging cyst is also seen, and in the deeper parts of the ectoderm are 
abundant, oval-shaped, deeply-staining bodies, evidently nematocysts in various 
stages of development, though some are granular gland cells. The endoderm 
contains an extraordinary quantity of granular pigment matter. 
The ectoderm of the stems (Pl. xmt., fig. 5) is devoid of nematocysts, and in 
structure is much like that of the column-wall, being highly glandular. A weak 
ectodermal musculature is supported on branching, mesogleeal processes. From the 
muscle fibres on these processes very delicate fibrils radiate in a peculiar brush- 
like manner. The muscle is better developed proximally than distally, and is 
practically absent from the knob. Internally the mesoglea forms deep, rounded 
plaits recognizable in longitudinal sections. The endodermal muscle is very 
weak, and the endoderm contains but little of the granular matter so abundant in 
the knob: the tissue nearly fills the lumen in retracted examples. 
The disc closely resembles the stem of the tentacles in structure ; the mesoglea 
2D 2 
